Pemanfaatan Ekstrak Daun Pepaya & Water Glass Sebagai Inhibitor Pada Baja St 37

St 37 is classified as low carbon content. St 37 has a tensile strength of about 3745 kg/mm 2 and a carbon value of about 0.468-0.574 %. One of the problems that St37 steel often faces is corrosion. There are several ways that have been conducted to reduce corrosion rate on metal materials, one of which is the addition of inhibitors. Papaya leaf can be used as a corrosion inhibitor because it contains tannins. These tannins have complex compounds that can be used as inhibitors to protect metals from corrosion. The purpose of this study was to examine the effect of papaya leaf extract and water glass on the corrosion rate of St 37 in salt water. The corrosion test was conducted in various inhibitor concentration i.e 0 ppm, 1500 ppm, 2000 ppm, 2500 ppm and 3000 ppm. The immersion time was 25 days and the corrosion rate was calculated based on materials weight loss at the 5, 10, 15, 20 and 25 days examination. The results show that corrosion rate continued to decrease for 15 and 20 days with different inhibitor concentrations. The lowest corrosion rate value was obtained at 2500 ppm inhibitor concentration with a time of 25 days, namely 0.0256 mm/y while the highest corrosion rate value was found on the materials without inhibitor addition (0 ppm) with a time of 5 days, namely 0.3336 mm/y. Inhibitor efficiency values continued to increase at concentrations of 2000 and 2500 ppm with a time of 10 to 25 days. The highest inhibitor efficiency value was at a concentration of 2500 ppm with a time of 25 days, namely 83.37% and the lowest inhibitor efficiency value was at a concentration of 1500 ppm with a time of 25 days, namely 16.68%